This invention relates to a method and apparatus for preparing hemodialysis fluids of accurately proportioned components. Particularly, the invention involves a method and apparatus suitable for preparing dialysate solutions for use in dialysis, ultrafiltration and the like.
It has increasingly been desired to easily and accurately control the concentration of a solution, in various chemical industries as well as in the preparation of various reagents and, in particular, of dialysate solutions for use in the control of metabolic functions, for example, in an artificial kidney system. In order to prepare such a dialysate solution of a constant concentration, there has hitherto been used a technique in which the amounts of concentrate and dilute fluid components are accurately measured separately by the use of a proportional feed pump and the like, and then, mixed together, as is described, for example, in U.S. Pat. No. 3,804,107. However, in such a technique, it is necessary to accurately measure the respective amounts of the concentrate and dilute fluid components and, thus, the necessary apparatus for the preparation of such a solution is inevitably complicated. Such a technique has further drawbacks in that a solution of an inaccurate concentration may often be produced, particularly when the difference in the amounts of fluid components is large, and when the mixing of the components occurs under a condition such that the components are in contact with a gas, such as air, thereby undersirably incorporating the gas into the resultant fluid.
Further, a patient in need of dialysis by an artificial kidney system must go to a hospital several times every week to receive lengthy hemodialysis treatments, which interferes with this return to a normal life. In order to make home treatment of the patient possible, it is necessary to provide a compact dialysis apparatus which can be operated easily and accurately, and thus, the development of such a compact, useful dialysis apparatus has earnestly been desired.
In U.S. Pat. Nos. 4,037,616 and 4,096,059, there is disclosed a method and apparatus for proportioning and mixing fluids utilizing a double acting piston/cylinder unit. However, in these patents, it is difficult to change the proportions of the components during the continuously repeated operations. Furthermore, in publicly disclosed Japanese Patent Application (Kokai) No. 72379/1977, there is disclosed a closed circuit simultaneous dialysis and ultrafiltration system.